In spasticity, rhizotomy precisely targets and destroys the damaged nerves that don’t receive gamma amino butyric acid, which is the core problem for people with spastic cerebral palsy. These over-firing, non-GABA-absorbing nerves generate unusual electrical activity during the EMG testing phase in SDR and are thus considered to be the source of the patient's hypertonia; they are eliminated with the electrical pulses once identified, while the remaining nerves and nerve routes carrying the correct messages remain fully intact and untouched. This means that the spasticity is permanently dissolved, and that this is done without affecting nervous system sensitivity or function in other areas, because the only nerves destroyed are the over-firing ones responsible for the muscle tightness.

The terms rhizotomy and neurotomy are also increasingly becoming interchangeable in the treatment of chronic back pain from degenerative disc disease. This is a procedure called a facet rhizotomy[4] and is not a surgical procedure but is instead done on an outpatient basis using a simple probe to apply radiofrequency waves to the impinged pain-causing nerve root lying between the facet joint and the vertebral body. Such radio frequency nerve lesioning results in five to eight or more months of pain relief before the nerve regenerates and another round of the procedure needs to be performed.[5] A facet rhizotomy is just one of many different forms of radiofrequency ablation, and its use of the "rhizotomy" name should not be confused with the SDR procedure.

Dorsal rhizotomy or selective dorsal rhizotomy (SDR), less often referred to as selective posterior rhizotomy (SPR), is the most widely used form of rhizotomy, and is today a primary treatment for spastic diplegia, said to be best done in the youngest years before bone/joint deformities from the pull of spasticity take place, but it can be performed safely and effectively on adults as well. An incision is made in the lower back just above the buttocks and the nerves accessed and dealt with are in that area of the spinal column.

SDR is a permanent procedure that addresses the spasticity at its neuromuscular root: i.e., in the central nervous system that contains the misfiring nerves that cause the spasticity of those certain muscles in the first place. After a rhizotomy, assuming no complications, the person's spasticity is usually completely eliminated, revealing the "real" strength (or lack thereof) of the muscles underneath. SDR's result is fundamentally unlike orthopaedic surgical procedures, where any release in spasticity is essentially temporary.

Because the muscles may have been depending on the spasticity to function, there is almost always extreme weakness after a rhizotomy, and the patient will have to work very hard to strengthen the weak muscles with intensive physical therapy, and to learn habits of movement and daily tasks in a body without the spasticity.

Rhizotomy is usually performed on the pediatric spastic cerebral palsy population between the ages of 2 and 6, since this is the age range where orthopedic deformities from spasticity have not yet occurred, or are minimal. It is also variously claimed by clinicians that another advantage to doing the surgery so young is that it is inherently easier for these extremely young children to restrengthen their muscles and to re-learn how to walk, often having the effect that later in life, they do not even remember the period of time when they lived with the spasticity at all. However, recent cases of successful SDR procedures among those with spastic diplegia across all major age ranges (years 3-40 and even above) has finally proven its universal effectiveness and safety regardless of the age of the spastic diplegic patient. A counter-argument against the prevailing view concerning the younger years is that it may actually be quicker and easier to restrengthen an older patient's musculature and regaining of walking may happen faster with an older patient due to the fact that the patient is fully matured and very aware of what is going on, and so may work harder and with more focus than might a young child. These two schools of thought have equally objectively-valid bases for their formation and thus are each defended quite intensely by their respective proponents.

In 1888, Robert Abbe in New York as well as W.H. Bennett in London independently performed the first dorsal rhizotomy in patients with ascending neuritis and sciatica, respectively. In 1898 C.S. Sherrington described relief of muscle spasticity by posterior root section in de-cerebrate cats. Between 1908-12 Harvey Cushing performed 3 dorsal rhizotomies to improve his patients’ quality of life.

The 1913 use in Germany of the rhizotomy procedure by Otfrid Foerster, often wrongly credited as the father of rhizotomy, was therefore actually not the first such use, since Sherrington’s studies were used as a basis for performing posterior root rhizotomy for the relief of spasticity in the lower limb muscles. Rhizotomy for spasticity purposes did indeed then proceed to take about a 50-year hiatus for reasons as yet not thoroughly distilled from the clinical records and reports on the phenomenon. An explanation for this could have been the fact that with the Sherrington/Foerster technique, postoperative sensory loss was too frequent, or by the fact that with their technique, spasticity often returned. In any case, it does appear as though rhizotomy for spasticity purposes continued to lie outside of any significant clinical use for the treatment of spasticity until its comparatively well-known turnaround to mild fame over the last quarter of the 20th century.

In 1964, a Dr. Wilkins wrote that this operation had “lost most of its original importance, but it still has historical significance as a major step in the development of modern techniques for the relief of pain."[citation needed] In 1967 Claude Gros and his colleagues at the neurosurgical hospital (CHU Gui de Chauliac) in Montpellier resurrected posterior rhizotomy for spasticity. Fasano of Italy in 1978 introduced 'selective' posterior rootlet rhizotomy for cerebral palsy patients and Warwick Peacock[6] developed the Gros technique at the Red Cross War Memorial Children's Hospital in Cape Town, South Africa, by exposing the cauda equina, rather than at the spinal cord level. Peacock moved to Los Angeles in 1986 and began campaigning rather widely for SDR's viability in cerebral palsy spasticity relief. Peacock and the surgeons he subsequently trained went on to develop the procedure further using both their own clinical-intellectual refinements and refinements in medical equipment and technology that occurred from the 1980s through the 2000s (decade).

Today, St. Louis Children's Hospital in St. Louis, Missouri has a "Center for Cerebral Palsy Spasticity" that is the only internationally-known clinic in the world to have conducted concentrated first-hand clinical research on SDR over an extended period. Its chief neurosurgeon in the field, Doctor T.S. Park (who was initially trained by Dr. Peacock), has performed thousands of SDR surgeries, some of them on adults, and is the originator of the L1-laminectomy modification to the SDR surgery in 1991, which sections the first dorsal root and enables the removal of significantly less spine-bone than in surgeries performed before 1991, as well as inherent release of the hip flexor muscles specifically as a result of that particular sectioning — prior to that, total hip flexor release was not necessarily possible. That L1-laminectomy modification has since become the standard method, and SLCH has become internationally known as a major provider of the SDR surgery to those in need of it; for example, it is one of the first Google search results when inputting the word string "selective dorsal rhizotomy". It is this clinic's opinion that patients with spastic diplegia or quadriplegia should have spasticity reduced first through SDR before undergoing muscle release or tendon release procedures, and other surgeons today share this view. A major qualifier in the cases taken on at SLCH, however, is that all of its adults have had only mild cases of spastic diplegia.

In September 2008, a SDR was performed that 'closed the gap' on concerns regarding age of the patient in SDR: Columbia-PresbyterianChildren's Hospital's Richard C.E. Anderson performed an SDR surgery on a 28-year-old male with moderate spastic diplegia, which by the patient's own report has reduced his muscle tone nearly to the level of a "normal" person and enabled him to walk and exercise much more efficiently; also, Dr. Anderson in the past performed an SDR on a 16-year-old wheelchair-using female with severe spastic diplegia. Reportedly, that particular SDR enabled the young woman to ambulate, whereas before the surgery, she was too tight to do so. In 2011, Dr. Anderson reported that another 16-year-old patient of his is considering undergoing the rhizotomy, but that patient subsequently decided to put her decision on hold[citation needed]. And in July 2011, after offering her several months of consultation, the medical team at the Continuing Care department of Gillette Children's Specialty Healthcare performed an SDR procedure on a local young-adult Minnesota resident.

Meanwhile, Drs. AV Dekopov, AA Tomskiĭ, VA Shabalov and EM Salova of the large Burdenkoneurosurgical clinic in Moscow, Russia are among those who advocate[7] strongly for the SDR procedure, including in adults, and the clinic lays claim not only to being the largest and most experienced SDR-performing clinic in Russia (probably analogous in that sense to the current status of St Louis Children's Hospital in the United States), but also to performing about 15 adult SDR procedures per year; these are all facts that until recently may have been almost entirely unknown outside of the Caucasus region.

The Chengdu and Shanghai areas of China have surgeons trained in SDR who perform the procedure successfully on adults. Also today, the clinical descendants of Warwick Peacock performing SDR in Cape Town typically continue to restrict their SDR procedures purely to children.

SDR begins with a 1- to 2-inch incision along the center of the lower back just above the waist. An L1 laminectomy is then performed: a section of the spine's bone, the spinous processes together with a portion of the lamina, are removed, like a drain-cap, to expose the spinal cord and spinal nerves underneath. Ultrasound and an x-ray locate the tip of the spinal cord, where there is a natural separation between sensory and motor nerves. A rubber pad is then placed to separate the motor from the sensory nerves. The sensory nerve roots, each of which will be tested and selectively eliminated, are placed on top of the pad, while the motor nerves are beneath the pad, away from the operative field.

After the sensory nerves are exposed, each sensory nerve root is divided into 3-5 rootlets. Each rootlet is tested with electromyography, which records electrical patterns in muscles. Rootlets are ranked from 1 (mild) to 4 (severe) for spasticity. The severely abnormal rootlets are cut. This technique is repeated for rootlets between spinal nerves L2 and S2. Half of the L1 dorsal root fibers are cut without EMG testing.

The neurosurgical team at Seattle Children's Hospital has modified the surgical approach described above by tailoring the selection of nerve root sectioning to the individual patient. This technique selectively analyzes each individual nerve root with electromyography to separate dorsal and ventral nerve roots through comparison of stimulus responses. Dr Samuel R. Browd, MD, PhD, and his team utilizes objective feedback from the nerve root compared to the above mentioned approach that relies on subjective visualization to identify motor versus sensory nerve roots, thus improving the likelihood of sectioning only those nerves of interest. Another important difference between the two approaches is the location of the laminectomy to expose the nerve roots. At Seattle Children's, the laminectomy is performed below the termination of the spinal cord (conus), potentially reducing the risk of injury.[8]

When testing and corresponding elimination are complete, the dura mater is closed, and fentanyl is given to bathe the sensory nerves directly. The other layers of tissue, muscle, fascia, and subcutaneous tissue are sewn. The skin is typically now closed with glue, but there are sometimes stitches to be removed from the back after 3 weeks. The surgery takes approximately 4 hours and typically involves one neurosurgeon, one anesthesiologist, and possibly an assortment of assisting physicians (as in the New York City September 2008 case). The patient then goes to the recovery room for 1–2 hours before being transferred to the intensive care unit overnight. Transfer from the ICU to a recovery room in the hospital is then done to enable direct post-surgical observation by the neurosurgeon and surgical team, but this usually lasts only about 3 days, during which the team performs range-of-motion tests that they record and compare to pre-surgery levels. After that short period, the patient, depending on circumstances and appropriateness, is either transferred to inpatient recovery or is linked to an intense outpatient exercise program and discharged from the hospital.

According to clinicians, it usually takes about one year from the date of surgery to achieve maximum results from SDR. However, videos from St. Louis Children's Hospital website have shown continued marked improvement as much as 5 years post-surgery, and presumably, if the person keeps exercising intensely, potential for continued improvement and strengthening is, just as in a person born with normal muscle tone and range of motion, unlimited.

Selective Dorsal Rhizotomy does not alleviate contractures caused by spasticity from before the surgery takes place; it simply prevents any more contractures or spasticity from occurring in future. With or without rhizotomy, the only way contractures can ever be relieved is via orthopaedic surgery. Fixed orthopaedic deformities of the legs caused by the previous years of intense spasticity are also not relieved by the nerve surgery and must also be corrected surgically. Whether or not to undergo such post-rhizotomy orthopaedic surgery depends on the circumstances of the rhizotomy recipient in question.

There is always abnormal sensitivity and tingling of the skin on the feet and legs after SDR because of the nature of the nerves that have been worked on, but this usually resolves within 6 weeks. There is no way to prevent the abnormal sensitivity in the feet. Transient change in bladder control may occur, but this also resolves within a few weeks.

If a certain degree of permanent numbness remains in certain leg-muscles, such as the quadriceps, ankles, and feet, this is usually not enough to prevent feeling and sensation, sensing of changes in temperature or pressure, etc. The affected muscle-areas simply feel less than before, and the trade-off in ease of movement is said to be immensely worth this change, should it occur.

In general, there is a combined 5-10% risk of any of the following more serious risks happening as a result of SDR. Because of technological advances in both the technology used in the surgery and also in the procedure itself, there have been no major cases of SDR that have had these side-effects.

After the surgery, all patients who were walking independently before surgery regained the independent walking within a few weeks after surgery. Patients maintain independent walking for the long term; when some have more difficulty walking independently they may eventually need an assistive device—however, in nearly all cases, spasticity can be eliminated and the quality of independent walking improves; in many patients, physical therapy and braces become unnecessary after SDR. Orthopedic surgery is rarely required after SDR.

In children who are 2–7 years old and walk with a walker or crutches before SDR, independent walking after the procedure is possible. Once they have achieved independent walking, they can maintain it.

In children who are older than 7 years and walk with crutches, independent walking (inside or outside house) is possible. If they walk with walker at the age, they will most likely walk with a walker or crutches after the procedure, though it improves the quality of assisted walking and transition movements, and alleviates deformities of the legs. Many of these patients will need orthopedic surgeries after SDR.

All candidates for rhizotomy must have good muscle strength in the legs and trunk. There must also be evidence of adequate motor control, or the ability to make reciprocal movements for crawling or walking, and to move reasonably quickly from one posture to another. Chiefly, pediatric rhizotomy candidates are people with CP who have shown age-appropriate progression in motor development, but spasticity hampers the development of skills and/or causes gait patterns like the scissors gait. In adults, the primary requirements are that the person is able to ambulate independently, but spasticity limits energy, flexibility, walking speed and balance and sometimes causes pain/muscle spasms.

There are a few clinical situations in which it is likely that someone may not be a candidates for the surgery. These situations include those who have suffered meningitis, a congenital (birth-originating) brain infection, congenital hydrocephalus unrelated to the person's premature birth, a person who has suffered head trauma, or a person with some sort of familial disease (e.g., those with hereditary spastic paraplegia are said to not be SDR candidates). Also precluded are people who have a "mixed" CP with predominant rigidity or dystonia, significant athetosis, or ataxia; and those who have very severe scoliosis. However, as with any procedure, an individual evaluation is needed in all instances to determine eligibility.

Most rehabilitation from SDR is done on an outpatient basis, though it may also include an initial several-week inpatient component (but typically does not). Typical base restrengthening and restoration of full ambulatory function takes about twelve weeks (3 months) of intensive physical therapy 4-5 times per week, but subsequent buildup and maintenance beyond that initial several-week period is just as necessary, and may require continued 4-5 times per week therapy as much as 6 months postoperatively, for a total of about a year and four months after surgery in order to achieve maximum basic functionary movement from the surgery. Beyond that point, any continued strengthening is, as with any person's exercise regimen, undertaken strictly by the individual's own choice and direction.

Support 4 SDR in Ontario Facebook Group/ Canadian based SDR support group run by parents for parents, who are looking for information on SDR, support with navigating the Ontario healthcare system and how to begin the SDR application process at The St Louis Children's Hospital, St Louis, Missouri "